Thermography

Thermography, or Thermal Imaging, or Thermographic testing is a non-contact, non-invasive, and hence non-destructive testing technique which is used to obtain thermal images of objects. These thermal images, also called thermograms, are colourful images depicting temperature distribution & variation on the surface of the test object. The variation in colour in different regions is an indication of corresponding temperature differences leading to flow of heat. Hence, hotter regions appear differently coloured than colder regions. This technique is based on the principle of Planck’s law of ‘black body radiation’ according to which every material above absolute zero (0 Kelvin) temperature emits infrared (IR) radiation, & the intensity of radiation depends on the temperature of surface emitting that radiation. This testing is accomplished using Infrared imaging cameras that can detect infrared radiations emitted by an object & convert them into visible images or thermograms. Such detections can indicate the thermal anomalies, also called ‘hot spots’ in any material substance and also in mechanical and electrical installation systems. Thermal imaging technology has become one of the most useful & valuable diagnostic tools for various industrial applications. It can detect & characterize any physical surface condition like voids, inclusions, de-laminations, crevices, cracks etc. by analyzing the differential heat flow patterns on the surfaces being tested.

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What are Infrared rays?

Infrared light is a substantial part or portion of the electromagnetic spectrum, and extends beyond the nominal red edge of the visible spectrum at 740 nm to 300 μm (or 300000 nm). It lies between the visible & the microwave region of the electromagnetic spectrum. Although human beings cannot detect IR light but they can realize it quite well. As per a scientific study, the nerve endings in human skin respond to temperature changes as small as 0.009 °C (0.0162 °F). This region of the spectrum can be divided into 3 sub-regions: near infrared (0.78 to 3 μm), mid infrared (3 to 50 μm), & far-infrared (50 to 1000 μm). The IR light is associated with the vibrational motion of molecules. The region from 8 to 15 μm is referred to as the ‘thermal imaging’ or ‘thermal infrared’ region, & is considered to be the optimum region for taking thermal images. The thermal imaging devices work best in this region. The credit of discovering IR radiation (in 1800) goes to a German astronomer Sir Frederick William Herschel, who measured the temperature differences of the spectrum created by making sunlight to pass through a prism & then based upon his observations concluded that the region beyond the red light marks the beginning of IR spectrum.

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Working of a Thermal Imaging Camera

Infrared thermography involves transforming or converting an infrared image into a radiometric one, and then the temperature values can be read from the image. The infrared radiation or energy coming from a test object is captured by an IR detector after being focused by the optics. The information from the detector is then sent to the sensor electronic system for image processing. Finally, the data from the detectors get translated into an image which can be viewed in the viewfinder or on a standard video monitor.

Applications of Thermography

Thermographic method of testing finds use in a number of industrial & other commercial applications like monitoring of high voltage power lines, internal fuse damage, damaged insulation, steam trap, corroded connections in electrical panel, overheated motor, water loss or leakage through ceilings, energy loss in buildings, damage in concrete, buildings & other constructions etc. Such monitoring facilities help in predicting failure of key components & also of entire systems in important machineries.

Some basic advantages of thermographic testing can be summarized as follows:
  • Safety, ease of operation, handling, and very less consumption of time.
  • Non-destructive nature of testing allows the integrity of test materials to remain intact.
  • Non-contact nature of testing makes it possible to monitor those substances which are either dangerously too hot or hazardous like high voltage electric wires.
  • Can be operated on test specimens during their functioning or while they are running
  • Can be operated on stationary as well as on objects in motion.
  • Can detect failing components, faults in a structure or machinery, corrosion or loose connections in an electrical system at an early stage, before such abnormalities become critical & lead to shut-downs and breakdowns in industries.
  • Can help prevent costly and unscheduled downtime problems, and serious accidents like outbreak of fire etc.
  • Can help in scheduling of ‘Preventive Maintenance’ programs for extending the ‘useful life’ of industrial machiner
  • In contrast to other NDT techniques which determine defects at particular points of testing, thermography provides a two-dimensional image of the test surface.

Spectro Analytical Labs Ltd. has been a pioneer service provider in the field of Non-destructive testing (NDT) for a long period of time. It comprises of an elite team of certified engineers who are not only well-trained & experienced in their respective field of work, but also possess a keen insight about the subject. Besides, Spectro possesses extremely modern & sophisticated thermal imaging instruments or cameras, which can provide superior quality thermal images because of finer details as a result of higher detector resolution. Hence, now Spectro can provide a highly improved & almost complete package of services in the field of NDT testing. In a nutshell, Spectro offers the following thermography services:

  • Electrical panel inspection
  • Identification of Transmission line problems
  • Furnace & refractory wall inspectionn
  • Energy auditing of buildings)
  • Cryogenic leak detection